1. Field of the Invention
The present invention relates to a filtering apparatus for engine exhaust, and in particular, to a filtering apparatus having a reusable filter element and a heat exchanger which is particularly well-suited to filtering diesel soot. A heat override valve and back pressure valve may also be included.
2. Description of the Prior Art
As concern for the environment increases, greater attention is being given to systems for eliminating damaging discharges from internal combustion engines. In the workplace, pollution created by combustion engines threatens the health of workers, as the particulate and other compounds contained in diesel exhaust may be carcinogenic. The problem is especially troublesome in enclosed environments such as warehouses or factories wherein diesel forklifts are often utilized. Fork lifts and other diesel engines are often operated in a cycling manner, that is, at maximum power for short periods which quickly raises engine and exhaust temperatures. Prior devices have not worked effectively during cycling to filter the exhaust. In addition, prior filtering units have generally been too expensive, ineffective, or too difficult to service.
Since the most efficient pleated filter material for filtering exhaust gases may have a maximum operating temperature, there must be safeguards to prevent the filter from igniting due to the hot exhaust gases. Therefore, when a predetermined temperature is exceeded, the exhaust gases must be redirected away from the filter to prevent combustion. Preferably, the problem of overheating is avoided by keeping the exhaust temperature below the ignition temperature of the soot and/or filter element. Prior devices have had no way of cooling the exhaust to prevent excessive temperature build up.
Should the exhaust temperature exceed a predetermined level, there has not been a satisfactory valving arrangement for redirecting the exhaust gases to prevent ignition of the filter element. Prior filtering apparatuses have not included temperature override devices to prevent filter ignition.
It can be seen then, that an improved filtering apparatus is needed which provides an effective reusable and replaceable filter element and which prevents overheating of the exhaust gases and includes safeguards to prevent ignition of the filter element.